code: def test_encode_categorical(df):
      df = df.encode_categorical("names")
      assert df["names"].dtypes == "category"
  
imports: import datetime
  import numpy
  import pandas
  import pytest
  from hypothesis import given, settings
  from pandas.testing import assert_frame_equal
  from janitor.testing_utils.strategies import categoricaldf_strategy, df_strategy
label_desc: Use image node_id 2 for calling a global function with example usage: test_encode_categorical(df) without return types